It the time of writing, it's still in beta. Hopefully, barring any further hiccups, it'll be released to the great unwashed on Monday 15th September, 2008.

StackOverflow is a Q&A site for developers. So what? Well, it's really slick. There's loads of activity, plenty of good questions and plenty more good answers. The way the site's been designed, it actively promotes high-quality content and discourages junk. I like it a lot.

If you can't wait until Monday (and I couldn't), there's information on how to access the beta on the blog.stackoverflow.com site.